CSS does not work like that. You do not need to use the div wrapping like that.

First of all you can give the wrapping div an ID or CLASS. Then you can target the child elements (The container for the small product layout you have) and then in your CSS stylesheet you can target that.

If your site is not responsive you can just give them a width for example and margin so that the margin looks something like this..

margin:10px auto 0 auto;

(Top Left Bottom Right)

Which will margin align elements central to that.

There are other methods but it will be based on the setup of your site code, the containers, how the sidebar is setup etc. Without a link that can only be guess work.